Gender differences in morality are thought to have evolved to adapt to different roles – women as being caring and compassionate to protect offspring, for instance, or valuing purity to protect monogamous relationships.

“It is important to women to invest resources in creating and maintaining supportive social networks in order to protect themselves and their offspring,” the authors note.

“For men, it can sometimes be attractive to invest their resources in forming coalitions to engage in intergroup aggression, as the spoils of an intergroup victory enhance their mating opportunities substantially.”

The fact that sex differences in the care factor dropped markedly in collectivist cultures could be explained by higher ratios of men to women, the researchers suggest.